1. Whisk together buttermilk and hot sauce in a large bowl. Add catfish. Cover and chill 24 hours.
2. Combine flour and next 3 ingredients. Remove catfish from buttermilk mixture, discarding mixture. Dredge catfish in flour mixture, shaking off excess.
3. Pour oil to depth of 1 1/2 inches into a large, deep skillet; heat to 325°. Fry catfish, in batches, 4 to 5 minutes on each side or until golden brown and fish flakes with a fork. Drain on a wire rack over paper towels. Sprinkle with salt to taste. Serve with additional hot sauce, if desired.